Researchers have used a computer program that simulates avian evolution to design a better flying machine. With further refinements, the contraption's offspring someday might flit like bats or birds.

For centuries, scientists and inventors have been attempting--nearly always unsuccessfully--to adapt the graceful beatings of a bird's wings for mechanical flight. A flapping craft would have two main advantages over planes and helicopters: It could stay airborne over a wide range of speeds and would be more maneuverable, achieving both without sacrificing aerodynamic efficiency. Such abilities could be particularly useful for unmanned aerial vehicles (UAVs), the lightweight aircraft the military increasingly employs for low-altitude reconnaissance.

Researchers from Pierre and Marie Curie University in Paris embarked on a unique strategy to apply the secrets of bird flight. They created a program called an evolutionary algorithm that essentially "evolves" a birdlike creature from scratch, refining designs that work and tossing those that don't. The team then appropriated the most successful designs from the algorithm to create a simulated UAV. The simulation achieved a birdlike energy efficiency flying at speeds between 10 meters and 12 meters per second, the researchers report in the December issue of Bioinspiration and Biomimetics. Based on the tests, the team has built a mechanical prototype with the goal, says biologist and lead author Emmanuel de Margerie, of improving wing designs based on further refinements from the algorithm.

Evolutionary roboticist Inman Harvey of the University of Sussex, U.K., praises the team's artificial evolution approach. It allows the exploration of designs "that a human designer might not have considered venturing into," he says. Still, the team's findings are limited, says research engineer Robert Michelson of the Georgia Institute of Technology in Atlanta. He notes, for example, that the simulated UAV the researchers developed is only efficient at relatively high speeds; at lower speeds, flight efficiency drops dramatically. And despite its advantages, flapping flight has its share of kinks. The bouncing reduces the value of the craft as a camera platform, says Michelson, and flapping can place large strains on wings. So far, these "have been the long poles in the creation of flapping-wing micro air vehicles," he says.